Serum peptides will be isolated from the equivalent of ten tons of cow serum. These peptides will be purified, their effects on the growth of cells determined and their primary structure determined. BIBLIOGRAPHIC REFERENCES: Sato, Gordon H. The Role of Serum in Cell Culture, Chapt. 11. Biochemical Actions of Hormones, Vol. III. 1975. (G. Titwack, ed.) Academic Press, Inc. Hayashi, I. and G.H. Sato. Replacement of Serum by Hormones Permits the Growth of Cells in a Defined Medium. 1976. Nature, 259: 132.